Micro-sample processing method, observation method and apparatus

a processing method and micro-sample technology, applied in material analysis using wave/particle radiation, instruments, nuclear engineering, etc., can solve the problems of reducing the throughput of the process, reducing the imaging resolution, and deformation at the observed portion, so as to reduce sample damage, suppress damage and deformation, and check the structure of the cross-section

Active Publication Date: 2008-11-20
HITACHI HIGH-TECH CORP
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  • Abstract
  • Description
  • Claims
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Benefits of technology

[0008]Display of the cross-section microstructure is possible by setting a strip-like processing region at an inclined portion of the sample cross-section, and enlarging the display on the processing monitor in a direction corresponding to a short-side of the strip-like processing region. It is then possible to check the structure of the cross-section without using an electron beam. Since it is possible to check the cross-section being processed without using an electron beam, the damage and deformation which would result from use of an electron beam on the cross-section being processed do not occur. By implementing the observation with a high-acceleration electron beam after creation of the thin film, it is possible to perform the observation with reduced sample damage, and then to fabricate an even thinner film using the FIB while observing a sample image resulting from an electron beam.
[0009]According to the present invention, it is possible to perform FIB cross-section processing and thin film processing while suppressing damage and deformation to a sample cross-section. Also, by combining the FIB with a high-acceleration SEM, STEM, and TEM, it is possible to observe the sample in which the damage and deformation have been minimized at a high resolution.

Problems solved by technology

The technological issue with regard to the micronization of the sample is to judge at what point to end the FIB processing, and to control the processing so that the portion to be observed is left over in the center of the thin film.
However, to realize microstructures having special electrical properties materials which are extremely sensitive to electron beam radiation, known as low-k materials, are widely used, and consequently there are many instances where sample broken or deformed by the SEM observation.
Method (1) has the disadvantage that time is required for cooling and exchanging samples, dramatically reducing throughput of the process.
Also, since electron-beam irradiation causes local damage, deformation will occur at the observed portion despite the cooling of the sample stage if the cooling path is insufficiently secure.
Method (2) has the disadvantage that the imaging resolution is lower by the reduction in the acceleration voltage of the electron beam, making it difficult to check the microstructure.

Method used

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first embodiment

[0032]FIG. 5 shows a construction of an FIB apparatus used in a first embodiment of the present invention. An FIB 3 generated by the FIB column 100 is focused on and scanned across a sample 1. Secondary electrons 2 emitted from the sample are detected by a detector 101, converted to digital values via a signal processing unit 112, and stored in an image memory in an image displaying unit 113. The storage to the image memory is controlled using a deflection address from a deflection signal generation unit 110. The apparatus includes an XY independent zoom ratio address converting unit 111, and is capable of altering display ratios for the X and Y axes independently.

[0033]FIG. 6 shows circuits surrounding the image memory of the image display unit. Changes to the zoom ratios and the addresses are realized by a digital adder and a barrel shift circuit. Further, a dual port memory which is capable of performing the reading and writing of data is asynchronously used as the image memory.

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second embodiment

[0037]FIG. 4 shows an image monitor window used in a second embodiment. In the second embodiment, the section view function includes a function for expansion of images in the x-direction as well as the function for the expansion of images in the y-direction. Moreover, the respective expansion ratios can be set individually. Hence, the display settings can be finely adjusted to match the sample, and judgments about the processing cross-section are simplified.

[0038]FIG. 4A shows the operation state of the standard processing monitor when the zoom ratios are “1” for both the x-direction and the y-direction. FIG. 4B shows the same section view display as in the first embodiment but with a y-axis zoom ratio of “8”.

third embodiment

[0039]The third embodiment describes an example in which the manufacture and observation of a thin-film sample are performed. The apparatus which was used is a compound apparatus having an FIB column 100 and an SEM column 150 installed in a same sample chamber. A gas source 170 for performing beam induced deposition and a manipulator 140 for handling the micro-samples are also installed in the sample chamber. Moreover, a large-sample stage 160 for holding and moving a sample 1 is installed in the sample chamber. Besides the sample 1, a thin-film carrier 10 for mounting the micro-sample obtained by the sampling is also mounted on the sample stage.

[0040]FIG. 8 illustrates the (micro-sampling) method, implemented in the third embodiment, for extracting from a region to be observed. First, a first deposition film 1 is formed by FIB-induced deposition at the region of interest in the sample 1 which is fixed to the large-sample stage 160. This was performed by supplying tungsten hexacarbo...

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Abstract

As sample sizes have decreased to microscopic levels, it has become desirable to establish a method for thin film processing and observation with a high level of positional accuracy, especially for materials which are vulnerable to electron beam irradiation. The technological problem is to judge a point at which to end FIB processing and perform control so that the portion to be observed ends up in a central portion of the thin film. The present invention enables display of structure in cross-section by setting a strip-like processing region in an inclined portion of a sample cross-section and enlarging the display of the strip-like processing region on a processing monitor in a short-side direction. It is then possible to check the cross-sectional structure without additional use of an electron beam. Since it is possible to check the processed section without using an electron beam, electron beam-generated damage or deformation to the processed section is avoided. Further, performing the observation using a high-speed electron beam after forming the thin film enables observation with suppressed sample damage. Processing of even thinner thin films using the FIB while observing images of the sample generated using an electron beam is then possible.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a micro-sample processing and observation technology using a focused ion beam.[0003]2. Background Art[0004]With the micronization of semiconductors, the need to observe and analyze microstructures has greatly increased. Focused Ion Beam (hereinafter abbreviated to FIB) apparatuses are capable of processing micro-samples, and can therefore be used, in particular, as sample pre-processing apparatuses for apparatuses capable of observing micro-samples, such as Scanning Electron Microscopes (hereinafter abbreviated to SEM), Scanning Transmission Electron Microscopes (hereinafter abbreviated to STEM), and Transmission Electron Microscopes (hereinafter abbreviated to TEM). Since FIB techniques allow the imaging of secondary particles (such as secondary electrons) generated by a sample and the setting of a processing region based on the images, it is possible to form a section at a desired poin...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G01N23/00
CPCG01N23/2255H01J37/244H01J37/3056H01J2237/30466H01J2237/30472H01J37/26
Inventor OHNISHI, TSUYOSHI
Owner HITACHI HIGH-TECH CORP
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